In certain large-scale printing systems, printheads are used to eject ink onto a substrate to create the desired image, for example, on substrates such as museum displays, billboards, sails, bus boards, and banners. In some of these printing systems, the printheads receive ink from an ink supply or reservoir and use so-called drop on demand ink jet process. With this type of process, ink is ejected from one or more nozzles of the printheads only when a piezoelectric crystal in the printhead is actuated. In particular, the piezoelectric crystal creates a pulse in the ink so that the ink expels through the nozzle as a droplet. To create the image, a carriage which holds one or more printheads scans or traverses across the substrate while the printheads deposit ink as the substrate moves. In some other systems, the substrate moves underneath a stationary set of printheads as the printheads deposit ink.
Generally, the printheads are under the direction of a controller or CPU. Stored within the memory of the controller or CPU is digital information related to the desired image. The controller operates with a software application that instructs the printheads to deposit ink in a particular sequence based on the stored digital information to generate a predetermined image on the substrate.
In some printing applications, a particular pattern is repeated within the image both across the substrate, as well as down the length of the substrate. However, the amount of digital information that would have to be stored in memory to produce the entire image can be quite large. Therefore, some have proposed storing information related only to the particular pattern, which would require significantly less memory than that required for the entire image, and then using a programmed image processing application to repeat the pattern in a tiling process.
However, because of certain constraints of image processing applications generally used to generate the images, as well as limitations in the raster image processor (RIP) applications that convert these images to a format the printer can understand, print-ready images can contain extraneous whitespace around the edges of the images. This whitespace, or dead space, around the image does not contain actual valid image data. In general, this does not pose a problem if only a single image is printed. Unfortunately, in printing applications in which it is desirable to repeat the image, for example, a repeated pattern on wall paper, curtains, floor tiling, or any other printed images with repeated patterns, as in a tiling operation, this whitespace shows up very clearly as “seams” in the final generated product. This unsightly seam is visible to an observer even when the whitespace is made of only one or two bits of blank data.